Question

What is the degree measure of an arc 4 ft. long in a circle of radius 10 ft.?

Answer 1

The length of an arc of a circle is given by the equation
L=Ar, where L is the arc-length, A is the angle made by the radius and some other radius used as a reference point, and r is the length of the radius.
So, to determine the degree measure of an arc, given the arc-length and radius, rearrange the equation to solve for A:
A = L/r

Answer 2

A is measured in radians (rad), by the way. 1rad = (360/2pi)degrees.